Effect of QMix irrigant on the microhardness of root canal dentine

Background The aim of this study was to evaluate the effects of QMix, EDTA + CHX, EDTA + NaOCl and maleic acid on the microhardness of root canal dentine. Methods Forty recently extracted human maxillary canine teeth were longitudinally sectioned into 80 segments and then embedded in an autopolymerizing acrylic resin. The microhardness of the dentine in the specimen was measured with a Vickers diamond indenter at the coronal, middle and apical thirds of the roots. Finally, the specimens were divided randomly into four groups: 17% EDTA + 2.5% NaOCl; 17% EDTA + 2% CHX; QMix; and 7% maleic acid. Post‐treatment microhardness values were obtained and the decrease in microhardness was calculated as a percentage. Microhardness values were statistically analysed using the Kruskal–Wallis and Mann–Whitney U tests. Results Maleic acid significantly decreased microhardness in all regions, compared to the other groups. In the coronal and middle regions, there was no significant difference among the other groups. In the apical region, there was no significant difference between QMix and 17% EDTA + 2% CHX but these groups presented significant dentine microhardness reduction compared to the 17% EDTA + 2.5% NaOCl group. Conclusions While maleic acid showed the greatest reduction in dentine microhardness, it was found that QMix, 17% EDTA + 2% CHX and 17% EDTA + 2.5% NaOCl cause the same reduction in the microhardness of root canal dentine in the coronal and middle regions.